The Vocal Warm-Ups Breath 

You don't need a singing voice for this! --But you may want privacy. The shower is the perfect location!

Start at a basic note (middle C is within most people's range). Hold for twelve seconds, then move up to C#. Hold for twelve seconds.
Repeat for the twelve notes to Bb. If desired, and you are able, repeat for another octave.

If you don't have a piano or other means of establishing pitch, just start at any note you are comfortable with, and raise the pitch until you've sung twelve notes.

When singers perform this exercise, they usually start by vocalizing "Ah", then "Eee", "Eye", "Oh", and "Oo",

If you want to really give yourself a workout, you can then try "Ah-ah-ah-ah-ah" on each note, really pushing out with your diaphragm. Follow this with "Eee-eee-eee-eee-eee" and so on. Concentrate on enunciating clearly as well as powerfully.